The field of the disclosure relates generally to ultrasonic inspection of structures fabricated from carbon fiber, and more specifically, to an inspection apparatus and method for irregular shaped, closed cavity carbon fiber structures.
One known aerospace structure includes a twenty foot long carbon fiber structure having a profile that is substantially trapezoidal in cross-section. To ensure integrity of the structure, an interior of this structure must be inspected. More specifically, the interior radii of this structure must be inspected due to the construction methods utilized in fabrication of the component. In the particular structure described herein, the cross-section of the trapezoid is less than 1.5 inches by 1.5 inches, though other cross-sections are contemplated.
As is known, the manufacturing of complex carbon fiber structures sometimes results in surfaces are not perfectly uniform across the length of the structure. This non-uniform surface is sometimes due to having a hard tool surface on one side of the carbon fiber ply stack up and a bladder surface on the other side during a curing cycle. The bladder occasionally allows one side of the stack up to vary. As a result, an inspection methodology and any apparatus used in inspection should account for these surface variations, while still maintaining a quality ultrasonic signal. Further, in a production environment, such ultrasonic inspection equipment must be robust enough to operate constantly for extended periods, for example, three working shifts within a 24 hour period.
While there are other methods and apparatus for inspection of such small profiles, such apparatus incorporate one or more of springs, shafts and bearings for positioning and orientation of the phased array transducers associated with the ultrasonic inspection equipment. Most of these ultrasonic probes require flat surfaces to index the mating surface of the probe for proper positioning of the ultrasonic transducer array. This method of using flat surfaces can and does skew ultrasonic “C-Scan” data in the event the surfaces of the part to be inspected are not consistent and flat.
Designing, assembling, and maintaining/repairing inspection probes that incorporate one or more of springs, shafts, bearings and other hardware to allow for the inspection of these inside surfaces is costly and time consuming. Moreover, relying on multiple components to position and orient the transducers adversely affects tolerances due to error accumulation. Ultrasonic testing is also sometimes performed in water environments. Hardware such as springs, shafts and bearings tend to corrode and/or fail over time. This down time of production equipment is costly to composite component manufacturers.